1. Technical Field
The invention relates to the field of voice over Internet protocol (VoIP) and more specifically to a system and method of terminating a VoIP call.
2. Description of the Related Prior Art
The growth and popularity of the Internet has facilitated voice over Internet Protocol (VoIP), the technology used to transmit voice traffic over a data network using the Internet Protocol. Such a data network may be the Internet or a corporate Intranet. Using the hardware/software integral to VoIP, users are able to use the data network as the transmission medium for telephone calls. Voice traffic is sent in IP packets rather than by traditional public switched telephone network (PSTN) circuits.
To connect an originating VoIP device with a destination VoIP device, an auxiliary IP-based protocol developed by the IETF known as Session Initiation Protocol (SIP) may be used. SIP is an application-layer control protocol that can establish, modify, and terminate multimedia sessions or calls with one or more participants. These multimedia sessions include, for example Internet telephony, and similar applications. FIG. 1 is a signal flow diagram depicting a typical call using SIP. At step 1) User A sends an INVITE to User B requesting session setup (i.e. for User B to participate in a media session). At step 2) User B responds with an informational message indicating that the SIP phone is ringing. At step 3) User B responds with an OK indicating that the User A request was successful. At step 4) User A sends an ACK request to confirm final response to the INVITE request. Following step 4) the media session occurs (e.g. the telephone conversation between User A and User B). At step 5) User B requests session termination by sending a BYE request. At step 6) User A responds with OK indicating the session has been successfully terminated.
In some cases, User B may be unable to request session termination because User B is unable to generate a BYE message. If this situation occurs, an alternate means of terminating the session is required.